A known electric cable has an electrically conductive (inner) conductor and an insulating sheathing of plastics material, which encloses the conductor along its length and electrically insulates it. The conductor can be a wire or a strand. In order to connect the electric cable with different electrical components (for example plugs, terminals) a part of the insulating sheathing can be removed at a cable end so that the bare conductor is exposed. The process of removal of the insulating sheathing is also termed stripping.
Industrial stripping of electric cables is usually carried out in a cable processing installation which is specially provided for that purpose and in which a knife of a stripping device initially cuts through the insulating sheathing in the region of a cable end and then pulls off the conductor the piece of insulating sheathing to be separated. During the stripping process the conductor of the electrical cable should not, if possible, be contacted or damaged by the knife.
Due to constantly increasing demands on quality in the mechanically executed stripping process it is necessary to monitor the stripping process. In that case it should be reliably detected whether a conductor of such an electric cable is damaged during this stripping process. Damage can consist of the conductor being cut into by the knife or even severed.
DE-A-10200753825 shows a stripping device for electric cables, which device comprises a capacitive sensor unit and an electrically conductive knife. The capacitive sensor unit is connected with the knife and constructed in such a way that contact of the conductive knife with a conductor of the cable can be detected on the basis of an increase in capacitance. The sensor unit comprises an alternating voltage generator which produces a sine signal. An internal resistance of the alternating voltage generator forms, together with the measured capacitance, a voltage divider so that the sensor unit can detect conductor contact on the basis of a reduction in the voltage amplitude of the sine signal. Such a stripping device has the disadvantage that contact detection on the basis of the sine signal can take place only slowly.